1. Field of the Invention
The invention relates to the shielding of the edges of electrodes used in electrolytic processes.
2. Description of the Prior Art
Electrowinning is an electrolytic process in which metallic ions, e.g., copper ions, are recovered from an electrolyte using anodes and cathodes in the form of generally rectangular plates. A large number of anodes and a large number of cathodes are suspended in the electrolyte vertically with the anodes and the cathodes alternating. The cathodes are typically made of titanium, stainless steel or a copper alloy, and the metallic ions deposit on the cathodes and coat them with sheets of pure metal. When the deposited sheets reach a certain thickness, the cathodes are removed from the electrolyte and the sheets stripped from the cathodes.
If deposition is allowed to occur at the edges of a cathode, metallic bridges are formed between the deposited sheets on either side of the cathode. These metallic bridges, which wrap around the edges of the cathode, make it difficult to strip the deposited sheets without damaging the sheets and/or the cathode.
To alleviate this problem, nonconductive strips known as edge strips or protector strips are placed over the submerged bottom and side edges of the cathode. These edge strips, which have identical cross sections, not only inhibit the formation of metallic bridges but also function to prevent direct contact between the cathode and the adjacent anodes.
At the lower corners of a cathode, the edge strips on the sides of the cathode define junctions with the edge strip at the bottom of the cathode. To prevent the penetration of electrolyte into, and an accompanying deposition of metal around, the junctions, U.S. Pat. No. 5,690,798 places a corner protector over each of the junctions. Each corner protector has two short legs which are perpendicular to one another, and each leg is provided with a channel having a cross section which matches the cross sections of the edge strips. One channel of each corner protector receives the adjacent end of the edge strip on the adjoining side of the cathode while the other channel receives the adjacent end of the edge strip on the bottom of the cathode. Each corner protector further has a cutout which runs between the free ends of the two legs of the corner protector and accommodates an adjoining portion of the cathode.
To prevent electrolyte from seeping into a corner protector, it is necessary to seal around the free end of each leg and along the two edges of the cutout. This rather extensive sealing is time-consuming.